This sort of material test is called a biaxial tensile test, and, for example, performed when measuring the strength of a metal plate. As such a material testing machine, Patent Literature 1 discloses a biaxial tensile testing machine in which each of two rails disposed in mutually orthogonal directions is movably provided with a pair of test piece chuck parts.
FIG. 15 is a perspective view illustrating a biaxial tension mechanism for applying test forces to a test piece 100 in such a conventional material testing machine.
The biaxial tension mechanism in this material testing machine includes a first rail 91 and a second rail 92 that are disposed on the surface of a base plate 90 in mutually orthogonal directions. The first rail 91 is slidably provided with a pair of first moving members 93. The pair of first moving members 93 is guided along the first rail 91, and thereby movable in directions to approach to and separate from each other along the first rail 91. Also, the pair of first moving members 93 is correspondingly provided with chucks 95 for grasping the test piece 100. On the other hand, the second rail 92 is slidably provided with a pair of second moving members 94 (in FIG. 15, only one is illustrated). The pair of second moving members 94 is guided along the second rail 92, and thereby movable in directions to approach to and separate from each other along the second rail 92. Also, the pair of second moving members 94 is correspondingly provided with chucks 96 for grasping the test piece 100. The base plate 90 supporting the first rail 91 and the second rail 92 is disposed on a base of the main body of the material testing machine.
Further, the biaxial tension mechanism includes a load member 80 that is connected to a crosshead of the material testing machine and applied with a load by the crosshead. The pair of first moving members 93 is correspondingly connected to the load member 80 through link members 83 including links 81 and links 82. The links 81 included in the link members 83 are swingably connected to the first moving members 93 by shafts 97 correspondingly, and the links 82 included in the link members 83 are swingably connected to the load member 80 by shafts 85 correspondingly. Further, the pair of second moving members 94 is correspondingly connected to the load member 80 through link members 84. One ends of the link members 84 are swingably connected to the second moving members 94 by shafts 98 correspondingly, and the other ends of the link members 84 are swingably connected to the load member 80 by shafts 86 correspondingly.
In the biaxial tension mechanism of the material testing machine, when the load member 80 is pressed in a state where the test piece 100 is grasped by the two pairs of chucks 95 and 96, the pair of first moving members 93 moves in the direction to separate from each other along the first rail 91 by the action of the link members 83 correspondingly, and the pair of second moving members 94 moves in the direction to separate from each other along the second rail 92 by the action of the link members 84 correspondingly. For this reason, the test piece grasped by the two pairs of chucks 95 and 96 is applied with tensile loads in two mutually orthogonal axial directions.